Generate a transcript for an asset, or for every asset in a folder.

Requires WRITE access on the asset or admin. The task no-ops when a transcript was already generated.

For a single asset, rejects types that cannot be transcribed with a 400. Pointed at a folder, it queues a walk of that folder instead and returns as soon as the walk is queued: task_id then tracks the fan-out, which dispatches one transcript task per asset. Types that cannot be transcribed are skipped there rather than rejected — a mixed folder is the normal case — as are assets the caller cannot write and assets whose media is not uploaded. The preflight route reports how many assets a folder would dispatch before you commit to it.

Unlike the description route this takes no config override: speech-to-text reads none of the tellers-config. One sent here is refused with a 400 rather than accepted and ignored, so a caller cannot believe a config applied to a transcript when nothing read it.